1. Field of the Invention
The invention relates to an area-light source module used in a liquid crystal display (LCD), and more particularly to a light emitting diode (LED) area-light source module used in an LCD.
2. Description of the Related Art
A Liquid Crystal Display (LCD) constitutes an LC glass cell, a color filter, and an area-light source module. The LC glass cell is used to control the display of patterns or characters. The color filter is used to provide a color combination from R, G, and B light. The area-light source module is used to achieve the display effects of uniformity, high transparency, and wide viewing angle. In accordance with the type of LCD, the area-light source module is defined as a back-light source module and a front-light source module. The back-light source module is set in the rear of the LC glass cell and the color filter, and is mainly applied to a transparent type LCD. The front-light source module is set in front of the LC glass cell and the color filter, and is mainly applied to a reflective type LCD or a transflective type LCD. The light source of the area-light source module includes a cold cathode fluorescent lamp (CCFL) serving as a linear light source, and a light emitting diode (LED) served as a point light source. The LED has advantages of low power consumption, long useful life and low cost, thus the LED area-light source module is popularly applied to middle-size LCDs and small-size LCDs in portable electronic products.
FIG. 1 is an exploded view showing a conventional LED area-light source module. An LED area-light source module 10 comprises a metal housing 12, an LED circuit board 14, an optical plate module 16 and a power supply 18. The metal housing 12 in constituting a flat base 20, a bending portion 22 and three raised portions 24. The bending portion 22 is an extension of one side of the flat base 20 and provides a lying space 23 therebetween for setting the LED circuit board 14, and the three raised portions 24 respectively protrude from the other sides of the flat base 20. The LED circuit board 14 comprises a plurality of LED chips 26 which are electrically connected to the power supply 18 through at least two wires 30. The optical plate module 16 comprises at least one light-guiding plate, at least one reflective plate and at least one diffusion plate to improve the intensity and uniformity of the area-light source and provide specific optical characteristics.
FIG. 2 is a top view of the LED circuit board 14 shown in FIG. 1. For electrically connecting the LED circuit board 14 to the power supply 18, one end of the wire 30 is welded to a connecting pad 28 on the LED circuit board 14, and the other end of the wire 30 is connected to the power supply 18. However, since the profile of the LED circuit board 14 is rectangular and the sidewall of the LED circuit board 14 adjacent to the connecting pad 28 is a faceted face, the exposed portion 31 of the wire 30 is exposed and can easy cause a short circuit.
FIG. 3 is a partially enlarged view showing an assembled structure including the metal housing 12, the LED circuit board 14 and the wires 30 shown in FIG. 1. In assembling the LED area-light source module, one end of the wire 30 is welded on the connecting pad 28 of the LED circuit board 14, and then the LED circuit board 14 is placed into the lying space 23 of the metal housing 12, and then the optical plate module 16 is stacked on the flat base 20 of the metal housing 12. However, during placement of the LED circuit board 14, it is easy to pull or drag the wire 30 due to the limitation of the lying space 23. Thus, the exposed portion 31 of the wire 31 may contact the adjacent metal housing 12, such as the flat base 20, the bending portion 22 and the raised portions 24, resulting in a short circuit.
Accordingly, an object of the invention is to provide an LED area-light source module used in an LCD to solve the short circuit caused by contact between the exposed wire and the metal housing in the prior art.
To achieve these and other advantages, the invention provides an LED area-light source module used in an LCD. A metal housing constituting a flat base, a bending portion, and at least one raised portion, in which the bending portion is an extension of the flat base and the overlapping portion between the bending portion and the flat base serves as a lying space. An LED circuit board is assembled into the lying space and has a plurality of chips, at least one connecting pad and at least one concave portion. The concave portion is formed at one rim of the LED circuit board and adjacent to the connecting pad. The concave portion constituting a bottom side and two sidewalls, and the bottom side is adjacent to the connecting pad. An optical plate module is assembled on the flat base of the metal housing. At least one wire has one end welded on the connecting pad and the other end connected to a power supply. An edge between the exposed portion and the unexposed portion of the wire is installed on the bottom side of the concave portion.